We are working on the implementation of an Infrared Laser Calorimeter aimed at the determination of the absolute heat capacity of proteins. The heat capacity is obtained through the measurement of thermal relaxation times of a protein solution at different temperatures. The calorimeter is designed as an adiabatic unit with two identical and absolutely transparent quartz cells. The cells (plane, cylindrical and 3.5 mm wide) are assembled in a thin hexagonal copper ring with their sides surrounded by thermal sensors of type RTD. The cells are placed in the interior of a cylidrical shell which has one small orifice on one of its faces connected to the optical fiber that constitute the guide for the laser. The inner region of the shell is covered by a thin metallic layer that has been polished and shrinked in order to reflect the laser light in every direction. A pulse of light is thus absorbed by the cell/sample assembly leading to an increase in the temperature of the system.